Could it possibly from one of the early SS pinballs (System 1-2) Aztec or Grand Prix prototypes?

Made a quick check @ipdb.org and from what I saw there the mystery driver board IS NOT from Rat Race (uses a System 7 mpu/driver boardset) nor any of the prototype pinballs as I hypothesised. It's either a (early)shuffle allley as Brakandl has guessed or it's something really rare (perhaps the mythical System 5?!?)

The earliest Williams shuffle alleys were released under the United label until about 1984. The games were:
Topaz (their first SS puck bowler/1978)
Pompeii(1978)
Aristocrat(1979)
King Tut (1979?)
Taurus (1979)
Omni (1980)
Big Strike (1983)
Triple Strike (last game built under the United name/1983)

I am convinced that it is most likely a driver board for one of the above games; note the 40 pin connector (which means that it uses a system 3-6 mpu) and it has from what I can see 15(?) transistors to drive solonoids (just enough to drive the pins, reset coil w/a couple left over). Lord knows that I'm not the most knowledgeable person on this but I cannot think of any other possibility.

What would REALLY help us out here is an original copy (not a reprint) of the parts manual from that period-I've got the reprint but the parts numbers for boards (along w/Defender arcade) are omitted.

Good guess....hadn't thought of that one.

Guess we'll won't be figuring this one out anytime soon...

Nice pics! Thanks! I'm gonna take at least one more guess and say that it's an early version of the 3-6 driver board (perhaps used in the solid state versions of Hot Tip and Lucky Seven?) and they made changes that made it into the board we're more familiar with?!? We know they changed stuff on the MPU and power supply boards why not with the driver board too?